This invention relates to wiper blades for automotive vehicles and the like, and more particularly, to a winter wiper blade which includes a protective rubber boot or sheath thereover.
The winter wiper blade, also known as a snow blade, has received much acceptance because of the advantages not only of preventing the entrance of snow and moisture into the articulated framework structure of the blade, but also of protecting the now common plastic components of the frame from the deleterious effects of the sun and various contaminants often present in the atmosphere.
To achieve these advantages, however, it is necessary to substantially completely enclose the frame or superstructure of the blade assembly; and this is difficult to do because of the complex nature of the structure and the fact that it must be left substantially unhindered by the sheath, so as not to affect the supporting and pressure applying characteristics of the assembly.
The problem of sealing the structure is further accentuated due to the fact that the wiper blade shape is typically enlarged in the central portion thereof and narrowed toward the ends, making it difficult to place a boot thereover, and further, that the wiper blade element itself, must be retained by the superstructure and yet be external of the rubber boot.
One example of prior art structure which describes this form of construction is shown in U.S. Pat. No. 2,727,271 wherein an articulated frame is enclosed in a rubber boot. Here the end portions of the boot are closed by rubber plugs which are retained by the backing strip for the wiper element. The backing strip is received in turn in claws in the supporting yokes and is subject to some endwise movement which could affect the seal between the boot and the plug. In similar prior art devices, it has been known to adhesively seal the end junctions of the rubber boots to adjacent structure, but it is apparent that this requires additional steps in the assembly process which is disadvantageous for high volume production.